• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.473-480
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• 1994

We have applied nonlinear interferometry of coherent anti-Stokes Raman spectroscopy (CARS) to measure the nonresonant third order susceptibilities of various gases. For the experiment, we placed two gas cells serially and filled the first cell with argon as a calibration standard and the second cell with gases under test. The interference fringes of the CARS signals generated in the two gas cells were obtained by changing the thickness of the phase shifting unit which was made of BK-7 glass. The total effective nonresonant susceptibilities were determined from the measured amplitudes of the interference fringes of the CARS signals of the gases. The nonresonant susceptibilities were obtained by subtracting off resonant vibrational contributions from the total effective susceptibilities. The results of this work are compared with the published data and the overall uncertainty is estimated to be less than 5%. an 5%.

• ETRI Journal
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• v.26 no.6
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• pp.635-640
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• 2004

A new low-complexity differential detection technique, fractional multi-bit differential detection (FMDD), is proposed in order to improve the performance of continuous phase modulation (CPM) signals such as Gaussian minimum shift keying (GMSK) and Gaussian frequency shift keying (GFSK). In comparison to conventional one-bit differential detected (1DD) GFSK, the FMDD-employed GFSK provides a signal-to-noise ratio advantage of up to 1.8 dB in an AWGN channel. Thus, the bit-error rate performance of the proposed FMDD is brought close to that of an ideal coherent detection while avoiding the implementation complexity associated with the carrier recovery. In the adjacent channel interference environment, FMDD achieves an even larger SNR advantage compared to 1DD.

• 순환기질환의공학회:학술대회논문집
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• 2006.04a
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• pp.28-36
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• 2006

The x-ray PIV method was improved for measuring quantitative velocity fields of real blood flows using a coherent synchrotron x-ray source. Without using any contrast media or seeding particles, this method can visualize flow pattern of blood by enhancing the phase-contrast and interference characteristics of blood cells based on a synchrotron x-ray imaging mechanism. The enhanced x-ray images were achieved by optimizing the sample-to-scintillator distance, the sample thickness, and hematocrit. The quantitative velocity fields of blood flows inside opaque tubes were obtained by applying a 2-frame PIV algorithm to the x-ray images of the blood flows. The measured velocity field data show typical features of blood flows such as the yield stress effect. The non-Newtonian flow characteristics of blood flows were analyzed using the x-ray PIV method and the experimental results were compared with hemodynamic models.

• International Journal of Vascular Biomedical Engineering
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• v.4 no.1
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• pp.1-8
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• 2006

The x-ray PIV method was improved for measuring quantitative velocity fields of real blood flows using a coherent synchrotron x-ray source. Without using any contrast media or seeding particles, this method can visualize flow pattern of blood by enhancing the phase-contrast and interference characteristics of blood cells based on a synchrotron x-ray imaging mechanism. The enhanced x-ray images were achieved by optimizing the sample-to-scintillator distance, the sample thickness, and hematocrit. The quantitative velocity fields of blood flows inside opaque tubes were obtained by applying a 2-frame PIV algorithm to the x-ray images of the blood flows. The measured velocity field data show typical features of blood flows such as the yield stress effect. The non-Newtonian flow characteristics of blood flows were analyzed using the x-ray PIV method and the experimental results were compared with hemodynamic models.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.234-237
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• 2003

The accuracy of channel estimation significantly affects the performance of coherent OFDM receiver. It is desirable to employ a good channel estimator while requiring low implementation complexity. In this paper, we propose a channel estimator that employs a simple two-dimensional (2-D) moving average (MA) filter as the channel estimation filter. The optimum tap size of the 2-D MA FIR filter is analytically designed in the time and frequency domain in association with the channel condition and pilot signal to interference power ratio. The analytic results can be applied to the design of adaptive channel estimator. Finally, the performance of the proposed channel estimator is verified by computer simulation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.1
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• pp.55-62
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• 1983

The error rate performance of phase shift Keyed(PSK) signal has been evaluated in terms of carrier-to-noise ratio(CNR), carrier-to-interferer ratio(CIR), impulsive index, and the phase difference between signal and interferer in the environment of cochannel PSK inter-ference and impulsive noise. We hays derived a general equation of the probability density function (p.d.f.) of output of coherent phase detector. And the error rate of the received binary PSK(BPSK) signal has been numerically evaluated. The graphic results show us that the best case is the situation of the signal and the inter- ferer meet with orthogonal phase.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.393-398
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• 2010

For multi-cell environments, coordinated random beamforming technique in multiuser MIMO(multiple-input multiple-output) broadcast channel is considered. In order to mitigate severe interference at receivers, the multi-cell environments might require complex transmitter and receiver design because the scheduler decision based on full channel state information (CSI) in one cell must be intertwined with decision made by other cells' CSI. With limited CSI, however, this paper considers a scheme of randomizing transmitters' beamforming but being coordinated with other cell transmitters. The transmitters in each cell share random beamforming patterns and schedule data transmission within coherent scheduling period. The corandomized beams allow the users to be selected with the highest SINRs even in multi-cell environments. We analyze the performance of the proposed scheme. And numerical results show that the scheme achieves better performance than the conventional random beamforming when applying to multi-cell environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1322-1331
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• 2000

In this paper, we compare the performance of noncoherent DS-CDMA system where orthogonal code is used for identifying the user to reduce multiple access interference or for M-ary orthogonal signaling to improve the performance of demodulation. The effects of M-ary orthogonal signaling on the noncoherent demodulation is investigated and compared with one of coherent demodulation. The analysis results show that M-ary orthogonal signaling gives better performance than quasi-synchronous orthogonal scheme for a moderate number of users when the processing gain is 128 over AWGN channel. In addition, when the number of user is 41, M=64 orthogonal signaling has a similar performance to the quasi-synchronous orthogonal scheme at the BER of 10-2 when the time misalignment between channels is within 1/2 chip and M=256 orthogonal signaling always outperforms the quasi-synchronous orthogonal scheme. Start after striking space key 2 times.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.4
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• pp.53-61
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• 2014

In this paper, we proposed covariance weight matrix using SPT matrix in order to accurate target estimation. We have estimated a target using modified covariance matrix and beam steering error method. We have minimized beam steering error in order to estimation desired a target. This method obtain optimum covariance weight using modified SPT matrix. This paper of proposal method is showed good performance than general method. We updated a weight of covariance matrix using modified SPT matrix. We obtain optimum covariance matrix weight to application beam steering error method in order to beam steering toward desired target. Through simulation, we showed that compare proposal method with general method. It have improved resolution of estimation target to good performance more proposed method than general method.

• Electronics and Telecommunications Trends
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• v.39 no.1
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• pp.48-61
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• 2024

The integration of high-capacity terrestrial networks with non-terrestrial communication using satellites has become essential to support seamless low-latency services based on artificial intelligence and big data. Tunable light sources have been instrumental in resolving the complexity of channel management in wavelength division multiplexing (WDM) systems, contributing to increased network flexibility and serving as optical sources for long-distance coherent systems. Recently, these light sources have been applied to beam-steering devices in laser communication and sensing applications across ground, aerial, and satellite transport. We examine the utilization and requirements of tunable lasers in WDM networks and describe the relevant development status. In addition, performance requirements and development directions for tunable lasers used in optical interference systems and beam-steering devices are reviewed.